In my earlier Austrian Pat. No. 346,707 issued Nov. 27, 1978, whose entire disclosure is herewith incorporated by reference, I describe a water-powered sprinkler wherein the pressure of the water ejected by the sprinkler is employed to displace it along the ground.
To this end the device has a chassis riding via wheels on the ground for entrainment by a hose which is laid down in the field to be irrigated in the path that the sprinkler should follow. The sprinkler is provided with an extensible bellows having a resiliently deformable inlet conduit connected via the hose to a supply of water under pressure and a similar outlet conduit connected to a sprinkler head, these conduits thus constituting extensions of the sprinkler hose. This bellows is biased by a spring into a compressed condition and the inlet and outlet conduits form with one or more blocking elements a duct assembly that alternately opens and closes the one conduit while closing the other.
The bellows is connected via a ratchet mechanism to the drive wheels of the chassis and also to a operating mechanism for the rotation of a valve body in a rigid housing surrounding the duct assembly. In addition, a reel on which the hose is wound as this device moves along the field is also powered via the one-way ratchet coupling by the bellows.
With this system when the inlet conduit feeding the bellows is open and the outlet conduit is closed, water under pressure flows into the bellows to expand it to a predetermined maximum size whereby the one-way ratchet coupling is stepped, e.g. in the direction in which it does not transmit rotation. Furthermore, during this expansion a heavy spring is loaded by the bellows.
At the end of the expansion of the bellows, the valve assembly is reversed to close off the inlet conduit and to connect the outlet conduit to the sprinkler heads. The biasing spring therefore compresses the bellows, forcing the water under considerable pressure out of the heads to sprinkle the field, and simultaneously stepping both the drive wheel and the hose-takeup reel. When the bellows is compressed to a predetermined minimum size, the valve is again reversed for repetition of the above-described cycle.
In such an arrangement it is therefore possible for the sprinkling apparatus to move around the field under its own power. No separate drive motor or the like need be provided for this sprinkler as it obtains all of the necessary energy for its displacement from the pressurized water fed to it. The liquid being sprayed by such an arrangement is not pure. In fact, the liquid is frequently laden with fertilizers, some of which do not dissolve completely but remain instead in particulate form. Furthermore, it is common practice to feed such a device via a pump directly from a stream or pond, in which case the water is relatively dirty. Hence, the machine is designed as much as possible to avoid passing this water through sensitive equipment.
In order to obviate the need for a delicate valve, whose seat could become fouled or damaged by foreign matter in the liquid passing through it, my above-cited Austrian patent 346,707 uses a rotatable valve body alternately flattening the input and output conduits against the sidewalls of a rigid valve housing; this valve body carries three angularly equispaced rollers. The valve housing is shaped so that, as the valve body rotates, at any given time one of the conduits will be flattened and the flow through it will be blocked whereas flow will be possible in the other conduit.
The problem with such an arrangement is that the conduits are subject to considerable wear by the periodic flexing and thus must be replaced often.